Air pollutants

Abstract

Asthma is a disease characterized by intermittent bronchoconstriction due to increased airway responsiveness to both allergic and nonallergic stimuli. Airways inflammation is a key underlying feature of this disease. Epidemiological evidence from the last two decades has shown that environmental pollutants such as ozone, PM, diesel exhaust (DE), and biological/microbial agents contribute significantly to the morbidity associated with asthma, including increasing exacerbation frequency. More recently, some pollutants, such as ozone, are now being implicated as causal agents in the development of new-onset asthma. Of note, the association between asthma exacerbation and air pollution has been reported at pollutant levels below the current ambient air quality standard. Moreover, studies have now focused on certain exposure locations, such as living near busy roadways or high traffic areas, as places of particularly high risk to suffer the deleterious effects of air pollution. As noted in the preceding case study, daily (Monday to Friday) exercise (bicycling) exposure near a busy urban roadway in combination with exposure to high levels of a specific allergen (birch pollen), was the likely cause of enhanced asthma exacerbations in a patient who, prior to this routine exposure, was symptomatically quiescent. Furthermore, in the absence of this exposure routine on weekends, her frequency of symptoms was significantly reduced. This case study draws our attention to the fact that air pollution may be affecting the airway’s host defense capability to allergens or equally feasible, and according to recent evidence, it may even augment exposure to airborne allergens.